NGC 1365
A double-barred spiral galaxy in the Fornax Cluster.
NGC 1365, called the Fornax Propeller Galaxy or the Great Barred Spiral Galaxy, is a double-barred spiral galaxy located roughly 56 million light-years from Earth in the constellation Fornax. Scottish astronomer James Dunlop first spotted it on 2 September 1826.
This large barred spiral belongs to the Fornax Cluster. At its center, a long bar stretches across the galaxy, and within that bar lies a smaller, inner bar measuring about 50 by 40 arcseconds in apparent size. This inner bar shows up more clearly in infrared images of the core. It likely forms from a mix of dynamical instabilities in stellar orbits, gravity, density waves, and the rotation of the galactic disc. The inner bar seems to spin faster as a whole than the larger outer bar, creating the diagonal appearance seen in pictures.
The spiral arms sweep north and south from the ends of the east–west bar, forming a nearly ring-like, Z-shaped halo. Astronomers believe the prominent bar plays a key role in the galaxy's evolution by funneling gas and dust into a star-forming frenzy and eventually feeding material into the central black hole. NGC 1365, including its two outer spiral arms, spans about 300,000 light-years. Different parts of the galaxy take different amounts of time to complete one rotation around the core; the outer bar takes roughly 350 million years to make a full circuit.
In recent years, NGC 1365 and similar galaxies have gained attention because new observations suggest the Milky Way might also be a barred spiral. Barred spirals are common—about two-thirds of spiral galaxies are barred, according to recent estimates—so studying them helps astronomers understand our own galaxy.
Four supernovae have been observed in NGC 1365. SN 1957C (type unknown, magnitude 16.5) was found by Howard S. Gates on 19 October 1957. SN 1983V (Type Ic, magnitude 13.5) was discovered by Robert Evans on 25 November 1983, and independently by P. O. Lindblad and P. Grosbol on 27 November 1983. SN 2001du (Type II, magnitude 14) was also found by Robert Evans, on 24 August 2001. SN 2012fr (Type Ia, magnitude 14.7) was discovered on 27 October 2012.
The galaxy’s active nucleus hosts a supermassive black hole with a mass of about 2 million Suns—roughly half the mass of the Milky Way’s central black hole, Sagittarius A*.
Quick Facts
- Epoch
- J2000
- Constellation Name
- Fornax
- Ra
- 03 · 33 · 36.4071
- Dec
- -36 · 08 · 24.669
- Z
- 0.005457 · 0.000003
- Dist Ly
- 74 Mly0.6774 / (Light-travel)
- Group Cluster
- Fornax Cluster
- Appmag V
- 10.3
Facts from the source article.
Lore & Background
NGC 1365 was discovered by Scottish astronomer James Dunlop on 2 September 1826. The galaxy features a large bar stretching across its center, within which a smaller bar comprises the core, with an apparent size of about 50 × 40. This inner bar is more prominent in infrared images and likely arises from dynamical instabilities of stellar orbits, gravity, density waves, and the overall rotation of the disc. The inner bar rotates more rapidly than the larger long bar, creating a diagonal shape in images. The spiral arms extend in a wide curve north and south from the ends of the east–west bar, forming an almost ring-like Z-shaped halo. Astronomers think the prominent bar draws gas and dust into a star-forming maelstrom and feeds material into the central black hole. Different parts of the galaxy take different times to complete a full rotation; the outer parts of the bar complete one circuit in about 350 million years. NGC 1365 and other barred spiral galaxies have come to more prominence with observations indicating that the Milky Way could also be a barred spiral galaxy. Such galaxies are common—two thirds of spiral galaxies are barred according to recent estimates.
Reader's Guide
NGC 1365 is significant as a nearby example of a double-barred spiral galaxy, offering insights into the dynamics of bar structures and their role in galaxy evolution. Its prominent bar is thought to funnel gas and dust toward the center, fueling star formation and feeding the supermassive black hole. The central black hole, with a mass of about 2 million solar masses, rotates at close to the speed of light, as observed by the NuSTAR X-ray telescope satellite in February 2013. Four supernovae have been observed in NGC 1365: SN 1957C (type unknown, mag. 16.5, discovered by Howard S. Gates on 19 October 1957), SN 1983V (Type Ic, mag. 13.5, discovered by Robert Evans on 25 November 1983 and independently by P. O. Lindblad and P. Grosbol on 27 November 1983), SN 2001du (Type II, mag. 14, discovered by Robert Evans on 24 August 2001), and SN 2012fr (Type Ia, mag. 14.7, discovered on 27 October 2012). The galaxy's location is one and a half degrees eastward of STAR 2, a telescopic asterism composed of Chi 1-2-3 Fornacis. Studying NGC 1365 helps astronomers understand barred spiral galaxies, including the Milky Way.
Did You Know?
- Its central supermassive black hole rotates at close to the speed of light.
- The galaxy spans about 300,000 light-years, including its two outer spiral arms.
- Four supernovae have been observed in NGC 1365 between 1957 and 2012.
More in Galaxy Clusters and Groups, Part 4 1-24
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